This invention relates to printers being fed continuous form media, and more particularly to printers having media drive mechanisms or paths exhibiting variable friction and tension effects on the media, thereby inducing jams of the printer feed or traction mechanism, or wrinkled or pealed surfaces of the media or the like.
A printer may be defined as an output unit that produces a hardcopy record of data mainly in the form of a sequence of discrete graphic characters that belong to one or more predetermined character sets. A printer may also be defined as a dual-path transducing system for mapping coded information on an alterable, permanent, visual medium of expression. A first path converts the information into a pattern of transducer actions for one-to-one alteration of the medium. A second path transports the medium to and provides a stable environment for the transducer to interact with and effectuate the permanent alterations or markings of the medium.
The second printer definition lends itself to emphasizing selective classification aspects of printers. For example, printers are classified according to whether the transducer alters the medium by impact or nonimpact means (first path) and whether the medium is discretely or continuously fed (second path). Indeed, for discretely fed printers, the medium is usually paper supplied to the printhead and platen a single sheet at a time. However, for continuously fed printers, the medium is usually a continuous length of a single-or multiple-ply, fan-folded paper with both edges punched for tractor feeding and with perforation between pages. Before printing, the forms are folded in a stacked arrangement with the folds along the perforation. The holes punched along both edges for tractor feeding are termed xe2x80x9ccarrier holesxe2x80x9d. Significantly, in continuous form printers, the xe2x80x9ctractorxe2x80x9d is the mechanism that controls movement of the continuous form paper by means of engaging the carrier holes with sprockets or the like.
There are many examples of continuous form printers such as the IBM 5417 and the IBM 5427. In continuous fed printers, the fan-folded forms are drawn either in straight form feed paths or curved form feed paths. These feed paths define the movement of the paper from its fan-folded position at one horizontal level to an unfolded extended position in the vertical direction at a higher level. In straight form feed paths, the tractor causes paper jams either by tearing apertures on the edges of the forms or by causing the pins to rotate without engaging the apertures. Since straight form feed paths lack any insertion guides, it is difficult for the operator to place the paper in such slit feeds to the tractor. In contrast, curved form feed guides assist the operator in feeding paper to the slit feeds of the tractor. However, such curved guides also increase the friction path in a vertical direction in the case where the fan-folded forms are each multipart forms of relatively heavy weight. Additionally, where the multipart forms consist of labels adhering to a support sheet, the curved feed paths tend to encourage peeling off of the label from a support sheet or encourage the formation of air pockets between the label and a support sheet. The former can cause a jam by wedging in the slit or tractor portions of the paper path. The latter, while not usually resulting in a jam, nevertheless wrinkles.
There are two prior art references of interest, namely, the Japanese published utility model applications S58-60463 and H6-246994. They both pertain to continuous form printing and are directed to the problem of removable print labels adhering to a substrate. The ""60463 reference discloses a method for preventing the peel off of a label from its supporting sheet. This is accomplished by pressing the labels to the supporting shape using a sheet-like guide during feed operations and an auxiliary guide plate for applying force to an upper surface of the label to conform the label to a concave shape. Unfortunately, in the ""60463 application, the labels are pressed to the supporting sheet after a layer of air is formed. Similarly, in the ""246994 application, the guide plate operates as a guide inside of the printer for switching a feed path between a continuous form feed path and a discrete sheet feed path. This, too, does not prevent the formation of air bubbles and the subsequent ring claim of the label.
It is accordingly an object of this invention to devise an apparatus and method to reduce friction and tension effects in the continuous form feeding of printers.
It is a related object that such apparatus and method mitigate such effects, especially on printers continuously form fed over curved form feed paths.
It is yet another object that such apparatus and method mitigate such effects, especially on printers continuously form fed with a continuous form multilayered medium where the print exposed layer of said medium is removably adherent to a substrate or support layer as is the case for substrate-mounted labels.
The foregoing objects are believed satisfied by a system for feeding a continuous medium to a processing station. The system includes a mechanism for moving the medium in a predetermined, vertically-oriented path over a guide toward the station. It further includes a guide mechanism for selectively altering the path length of the medium in relation to the guide in a direction toward minimizing the friction resistance between the medium and the guide.
In the system, the continuous medium is selected from the set consisting of a single-ply fan-folded paper, multiple-ply fan-folded paper, and multiple-ply paper with alterable labels adhering to support sheets. Furthermore, the guide mechanism includes an arrangement for selectively positioning the guide in either a first or second position. The first position defines a first path length of predetermined curvature including the guide in contact relation with the medium. The second position defines a straight form frictionless feed path between the medium and the guide. Any intermediary position defines a proportionally reduced friction path. Relatedly, the mechanism includes an arrangement for engaging the medium and urging it toward the processing station. The arrangement is selected from a set consisting of sprockets engaging an edge-perforated medium and a pair of pinch rollers forming a pressure contact engagement with said medium.
The positioning of the guide can be implemented through operator manual intervention or through a motorized and sensor-driven automatic system. Also, the guide can be formed from elastic as well as inelastic materials.